Communication system, communications device, infrastructure equipment and method of allocating resources for performing device-to-device(D2D) communication

ABSTRACT

A communications system comprising a plurality of a communications devices and an infrastructure equipment. The infrastructure equipment is configured to communicate with one or more of the plurality of communication devices via a wireless access interface and the plurality of communications devices are configured to perform device-to-device communication with one or more others of the plurality of communications devices via the wireless access interface and to communicate with the infrastructure equipment via the wireless access interface. One of the plurality of communications devices is configured to transmit data in resources of the wireless access interface to one or more of the communications devices and one or more of the communications devices are configured to detect signals in the wireless access interface from the infrastructure equipment, the signals indicating potential interference in the wireless access interface, and to provide, in response to detecting the signals, an indication of the resources of the wireless access interface to the infrastructure equipment.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based on PCT filing PCT/EP2014/073151 filedOct. 28, 2014, and claims priority to European Patent Application 13 191226.3, filed in the European Patent Office on Oct. 31, 2013, the entirecontents of each of which being incorporated herein by reference.

FIELD OF THE DISCLOSURE

The present disclosure relates to communications systems, communicationsdevices infrastructure equipment and methods of device-to-devicecommunications.

BACKGROUND OF THE DISCLOSURE

Third as well as fourth generation mobile telecommunication systems,such as those based on the 3GPP defined UMTS and Long Term Evolution(LTE) architecture are able to support more sophisticated services thansimple voice and messaging services offered by previous generations ofmobile telecommunication systems.

For example, with the improved radio interface and enhanced data ratesprovided by LTE systems, a user is able to enjoy high data rateapplications such as video streaming and video conferencing on mobilecommunications devices that would previously only have been availablevia a fixed line data connection. The demand to deploy fourth generationnetworks is therefore strong and the coverage area of these networks,i.e. geographic locations where access to the networks is possible, isexpected to increase rapidly.

The anticipated widespread deployment of fourth generation networks hasled to the parallel development of a class of communications devices andapplications which, rather than taking advantage of the high data ratesavailable, instead take advantage of the robust radio interface andincreasing ubiquity of the coverage area. One example of such anapplication is public safety communications, for instance communicationsbetween members of the emergency services. Public safety communicationsrequire a high degree of robustness and therefore fourth generationnetworks provide cost effective solution to public safety communicationscompared to dedicated systems such as TETRA which are currently usedthroughout the World. However, for public safety applications it ishighly desirable that public safety communications devices can stillcommunicate with each other even when outside of a coverage areaprovided by an LTE system. In LTE release-12 the ability for LTE devicesto perform device-to-device communications has been introduced. Thistherefore allows LTE device to communicate with each other when outsideof a coverage area but within close proximity of one another. Thisdevice-to-device communications ability allows LTE public safetycommunications even when there is no network coverage. However, the useof LTE for both high-reliability public safety communications andcommercial applications may lead to complex resource allocation.

SUMMARY OF THE DISCLOSURE

According to an example embodiment of the present disclosure there isprovided A communications system comprising a plurality of acommunications devices and an infrastructure equipment. Theinfrastructure equipment is configured to communicate with one or moreof the plurality of communication devices via a wireless accessinterface and the plurality of communications devices are configured toperform device-to-device communication with one or more others of theplurality of communications devices via the wireless access interfaceand to communicate with the infrastructure equipment via the wirelessaccess interface. One of the plurality of communications devices isconfigured to transmit data in resources of the wireless accessinterface to one or more of the communications devices and one or moreof the communications devices are configured to detect signals in thewireless access interface from the infrastructure equipment, the signalsindicating potential interference in the wireless access interface, andto provide, in response to detecting the signals, an indication of theresources of the wireless access interface to the infrastructureequipment.

In one example, the potential interference is in an uplink channel ofthe wireless access interface.

In one example, in response to receiving the indication of the resourcesof the wireless access, the infrastructure equipment is configured toreallocate resources of the wireless access interface to compensate forthe interference.

In one example, in response to receiving the indication of the resourcesof the wireless access, the infrastructure equipment is configured toprovide a resource reallocation message to the data transmittingcommunications device, and the data transmitting communications deviceis configured, in response to receiving the resource reallocationmessage, to transmit data in resources of the wireless access interfacein accordance with the resource reallocation message to compensate forthe interference.

Providing a mechanism by which communications devices may indicate to aninfrastructure the resources which they using that are experiencinginterference, allows the infrastructure equipment to reconfigureresource allocations. This is turn allows interference which is dueoverlapping resources used by the infrastructure equipment and thecommunications devices to be reduced.

In one example one of the communications devices forms a controllingentity for allocating the resources of the wireless access interface tothe communications devices.

In one example, in response to receiving the indication of the resourcesof the wireless access, the infrastructure equipment is configured toprovide a resource reallocation message to the controlling entity, andthe controlling entity is configured, in response to receiving theresource reallocation message, to reallocate resources of the wirelessaccess interface in accordance with the resource reallocation message tocompensate for the interference.

Providing a resource reallocation message to a controlling entity allowsa centralised and coordinated resource reallocation to take place asopposed to each communications device being required to independentlyperform the resource allocation.

In one example the detected signals are in a downlink channel of thewireless access interface from the infrastructure equipment, and thedownlink channel of wireless access interface and an uplink channel ofthe wireless access interface from the communications devices include atleast some of the same resources.

This allows the communications device to identify signals that may causeinterference in the uplink of the device-to-device communications byreceiving a downlink signal from the infrastructure equipment. Thereforethe communications devices may not be required to establish a connectionwith the infrastructure equipment in order to establish whetherinterference may occur.

In one example the indication of the interference is provided inresponse to the signals in the wireless access interface interferenceexceeding a predetermined threshold.

The use of a threshold reduces the possibility that resources areunnecessarily reallocated in scenarios were the interference isinsufficient to affect the device-to-device communications within thegroups of communications devices. Thus potentially reducing controloverheads at the controlling entities.

Various further aspects and embodiments of the disclosure are providedin the appended claims, including but not limited to a communicationsdevice, infrastructure equipment and a method of communicating

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will now be described by way ofexample only with reference to the accompanying drawing in which likeparts are provided with corresponding reference numerals and in which:

FIG. 1 provides a schematic diagram of a mobile communications system;

FIGS. 2a and 2b provides schematic diagrams of device-to-devicecommunications systems;

FIGS. 3a to 3d provides schematic diagrams of coverage scenarios indevice-to-device communications systems;

FIG. 4 provides a schematic diagram of a coverage scenario in adevice-to-device communications system;

FIG. 5 provides a schematic diagram of a coverage scenario in adevice-to-device communications system;

FIG. 6 provides a flow diagram of an interference mitigation techniquein a device-to-device communications system;

FIG. 7 provides a flow diagram of an interference mitigation techniquein a device-to-device communications system;

FIG. 8 provides a flow diagram of an interference mitigation techniquein a device-to-device communications system;

FIG. 9 provides a flow diagram of an interference mitigation techniquein a device-to-device communications system;

FIG. 10 provides a flow diagram of an interference mitigation techniquein a device-to-device communications system;

FIG. 11 provides a schematic diagram of a coverage scenario in adevice-to-device communications system; and

FIG. 12 provides a schematic diagram of a coverage scenario in adevice-to-device communications system.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1 provides an illustration of a conventional mobile or cellularcommunications network where network infrastructure equipment 101, suchas an enhanced node B (eNodeB) in an 3GPP long term evolution (LTE)system, provides a wireless access interface to one or more mobilecommunications devices 102 103, which may also be referred to as userequipment (UE). Within a coverage area an eNodeB is configured toallocate uplink and downlink resources of a wireless access interface tothe UEs such that they can communicate with each other via the eNodeB.These resources may be defined in terms of frequency and time and mayalso be time varying. The wireless access interface extends across apredetermined bandwidth, which for example in LTE systems is between 1.4MHz and 20 MHz, and the wireless access interface in the case of LTEsystems may be provided in the downlink by orthogonal frequency divisionmultiplexing (OFDM) and in the uplink by single carrier frequencydivision multiple access (SC-FDMA). However, in other communicationssystems the bandwidth allocations and wireless access interface maydiffer.

FIG. 2a illustrates a scenario where two UEs 201 and 202 may communicatewith each other directly, i.e. without the need for infrastructureequipment. In LTE this technique is termed device-to-device (D2D)communications and was introduced into LTE release-12. As opposed torequiring an eNodeB to provide and allocate the resources of a wirelessaccess interface, the UEs communicate directly with each other bynegotiating access to a wireless access interface directly, althoughthey are still also operable to communicate with infrastructureequipment. The wireless access interface may be provided in accordancewith any of a number of techniques such as carrier sense multiple access(CSMA), OFDM or a combination thereof for example. Although in theforegoing description D2D communications are described with reference toan LTE system, the proposed techniques are equally applicable to othersystems which are compatible with D2D communications.

D2D communications may use spectrum resources allocated to a networkwhich the UEs are compliant with i.e. conventional LTE spectrum, or mayuse an independent licensed or unlicensed portion of spectrum.Advantageously, D2D communications devices may communicate with eachother whilst not being within a coverage area of an eNodeB.Additionally, even if within the coverage area of an eNodeB the closeproximity of the UEs may allow high data rate communications to beperformed without the eNodeB taking part in the allocation of resources,thus freeing-up eNodeB resources. D2D communications may also providebenefits in terms of energy consumption at UEs. For example, if two UEsthat wish to communicate with each other are in close proximity but inthe outer regions of a coverage area, reduced power transmission may berequired for D2D communication than for conventional communications viathe serving eNodeB. Although in FIG. 2a only two UEs have beenillustrated, any number of UEs may take part in D2D communicationsprovided that they are within range of each other. A group of UEs thatare within D2D communication range of each other may be referred to as aD2D group.

FIG. 2b illustrates an alternative D2D communications technique. Incontrast to FIG. 2a , a UE 211 acting as a controlling entity (CE) isrequired to coordinate the communications between “slave” UEs 212 213 byallocating resources to the UEs which intend to communicate with eachother, as well as in some examples acting as a relay between UEs whichcannot communicate directly. The controlling entity may be one of theUEs intending to communicate, another UE from the D2D group or may be aspecially adapted UE. The role of a controlling entity is to allocateresources, schedule communications between the UEs performing D2Dcommunications and manage any interference that may be encountered.Accordingly, it is beneficial if the controlling entity is able tocommunicate with the maximum number of UEs. The controlling UE for a D2Dgroup may change over time as UEs move and enter and exit a coveragearea provided by a particular controlling entity or the controllingentity itself moves. For example, if a currently controlling entitymoves such that a second UE becomes able to communicate with highernumber of UEs by virtue of being in a more central geographic positionrelative to the other UEs, the role of controlling entity may betransferred to the second UE. A coverage area provided by a controllingentity may also define a D2D group, whereby UEs which can communicatewith a particular controlling entity fall within a same D2D group.However, a D2D group may also be defined as UEs which are within acoverage area of a specified controlling node and which also wish toperform D2D communications.

D2D communications are anticipated to be used for a number ofapplications, which may include high data rate short-rangecommunications and public safety or emergency communications whereemergency personal communicate via the use of UEs. For example, if anemergency occurs in any area where there is no or limited networkcoverage or as a result of the emergency network coverage has been loste.g. due to an earthquake, it is important that emergency personalmaintain the ability to communicate with each other without the need forinfrastructure equipment. Accordingly, in emergency scenarios it may berequired that public safety D2D communications take priority overcommercial communications.

UEs which are operable to perform D2D communications are alsoanticipated to be operable to communicate with conventionalinfrastructure equipment such as eNodeBs. Consequently, UEs inrelatively close proximity may communicate via D2D communications whenthey are outside of a coverage area of an eNodeB and communicate viaconvention LTE communications when within the coverage area of aneNodeB. Although this dual communication ability provides increasedrobustness, this may lead to increased complexity wireless accessinterface resource allocation. As previously mentioned, the resourcesthat UEs will use to perform D2D communications may vary. For instancein some examples they may utilise resources in unlicensed bandwidth suchas the ISM 2.4 GHz band. However, in other examples the UEs will utiliseresources in the bandwidth allocated to the LTE networks for D2Dcommunications. Although the use of licenced bandwidth is likely toavoid a proportion of the interference that may be present in the ISMbands, the issue of how to allocate resources between conventional LTEcommunications and the D2D communications arises.

As described above, D2D communication may be utilised for public safetycommunications, which are high priority communications. Consequently, itis important that resources for D2D communications are available as andwhen required. A number of approaches to resource allocation arecurrently proposed depending on the position of UEs relative to eNodeBcoverage. For example, a predetermined portion of the bandwidth/spectrumof the network which the UEs are members of may be reserved solely forD2D communications. This will therefore help ensure that whether UEs areoutside or within a coverage area of an eNodeB there will be sufficientresources available for D2D communications. However, although thisapproach may increase the probability that resources will be availablefor D2D communications, this may lead to inefficient use of resourcesfrom a network operator perspective because the reserved resources willnot be available to be used by the eNodeB when D2D communications arenot taking place. A second approach is for an eNodeB to take part in theD2D resource allocation when D2D operable devices are in its coveragearea such that any resource may be selected for D2D communications.However, this does not address the scenario where the UEs are outside ofa coverage area. The first and second approaches may also be combined sothat an eNodeB allocates resources to UEs for D2D communications from apredetermined set of resources and if a UE is not within a coverage areathe UE selects resources from a predetermined set known to the eNodeB.

Device-to-Device Communications Usage Scenarios

As a result of the communication techniques (D2D and conventionalcellular communications) in the LTE system described above, a number ofdifferent coverage scenarios may occur, each of which may impact on thechoice of resource allocation procedure. Furthermore, in some scenariosthe resource allocation techniques described above may not besufficiently flexible to balance the requirements of D2D devices, andparticularly public safety D2D devices, against the commercial interestsof the network operators which support the D2D UEs.

FIGS. 3a to 3d provide illustrations of scenarios that may occur in LTED2D communications and the impact that the various scenarios may have onresource allocation.

FIG. 3a illustrates the scenario where two UEs 301 302 are not withinthe coverage area of an eNodeB and are communicating via D2Dcommunications. Due to lack of eNodeB coverage the network is unlikelyto be able to take an active part in any resource allocation procedure.Additionally, because the UEs are not in a coverage area, the use ofnetwork resources (i.e. a portion of network bandwidth) for D2Dcommunication is unlikely to impact upon the capacity of the network.

FIG. 3b illustrates the scenarios when one of two UEs 311 312 which areperforming D2D communications is within the coverage area of an eNodeB313. Consequently, the UE within the coverage area may communicate withthe eNodeB and communicate with the second UE via a wireless accessinterface adapted for D2D communications. Due to the ability of one ofthe UEs to communicate with the eNodeB the network may take an activerole in determining the resources allocated for D2D communicationsbetween the UEs and the resources used for D2D communication may impactupon resource allocation at the eNodeB.

FIG. 3c illustrates the scenario where UEs 321 322 are performing D2Dcommunications and they are both within the coverage area of the sameeNodeB 323 such that the UEs may communicate with each other via theeNodeB or via D2D communications. As for FIG. 3b , the eNodeB istherefore able take an active role in the allocation of resources forthe D2D communications and the resources used for D2D communication mayimpact upon resource allocation at the eNodeB.

FIG. 3d illustrates the scenario where the UEs 331 332 performing D2Dcommunications are each within the coverage area of a different eNodeB.The first UE 331 is operable to communicate with both the second UE 332and a first eNodeB 333 and the second UE 332 is operable to communicatewith both the first UE 331 and the second eNodeB 334. Consequently, theUEs may communicate with each other either via the eNodeBs or via D2Dcommunications. When D2D communications are chosen the network may onceagain take part in the resource allocation because at least one UE iswithin the coverage area of an eNodeB and the resources used for D2Dcommunication may impact upon resource allocation at either of theeNodeBs.

In the scenarios of FIGS. 3b to 3d , the network may take an active rolein D2D resource allocation because least one of D2D UEs are within thecoverage area of an eNodeB. Furthermore D2D communications may impactupon network allocation at the eNodeB because they are within the eNodeBcoverage area. In the scenario of FIG. 3a the resources used for D2Dcommunications will not impact upon non-D2D resources because the D2Dcommunications are taking place outside of network coverage. However, ifD2D resource allocation initially takes place in a scenario as depictedin FIG. 3a but the UEs move such that a scenario as depicted in any ofFIGS. 3b to 3d occurs, resource allocation problems may occur becausethe initial resource allocation has not taken into account the presenceof an eNodeB. This scenario is depicted in FIG. 4.

In FIG. 4 a D2D communication group is formed from a plurality of UEs401 to 404 where UE 401 is the controlling entity, or a transmitting UEif a controlling entity is not present and direct D2D communications aretaking place, and provides a coverage area 405 for the D2D communicationgroup. The eNodeB 406 provides a network coverage area 407 in which UEsmay perform conventional LTE communications with the eNodeB. As shown inFIG. 4, UE 403 may move into the interference region 408 from outsidethe coverage area 407 whilst maintaining its membership of the D2Dcommunication group. Consequently, if the resources utilised by the D2Dgroup and the eNodeB overlap, there may be increased interference andpotential failure in D2D communication and/or the eNodeB communications,which in the case of public safety applications is unacceptable.

A similar situation may also occur when two D2D groups of UEs move withone another's coverage areas. This scenario is depicted in FIG. 5. Afirst group of UEs 501 to 504 are within the D2D coverage area 505provided by a first controlling entity UE 501, or a transmitting UE if acontrolling entity is not present. A second group of UEs 506 to 510 arewithin the D2D coverage area 511 provided by a second controlling entityUE 506. Initially these the coverage areas of the first and secondgroups do not overlap and the D2D communications within each group areunlikely to interfere with each other. However, as shown in FIG. 5, if amember of the first group moves into the coverage area of the secondgroup (i.e. the interference region 512) and the wireless resources ofthe two groups overlap, increased interference will be experienced inthe wireless access interface by both the first and second groups. Thismay lead to degraded perform and potential failure in D2Dcommunications, which for public safety applications is once againunacceptable. In order to reduce the possibility of increasedinterference and D2D communication failure, a mechanism by which theproblem of overlapping resources can be resolved would be beneficial.

Device-to-Device Communications Resource Allocation

FIG. 6 provides a flow diagram of generalised approach to addressing theproblems of resource overlap described above. Initially a resourceallocation message 601 is provided to the UE by its controlling entity(if one is present) where the message 601 indicates the resources thatthe UEs are to use for D2D communications. If a controlling entity isnot present a UE may just start transmitting in resources if theresources are determined to be free from a carrier sense operation.Accordingly, a receiving UE will detect such a transmission are proceedto receive it. Whilst D2D communications are being performed by the UEs,each UE monitors its allocated resources for interference. Onceinterference is detected from an interfering entity such as aneighbouring D2D group or an eNodeB at 602, the UE is required tocompensate/avoid the interference. The UE has one of two options on howto compensate for the interference. As will described in more detailbelow, depending on the origin of the interference, the UE may providean indication 603 of the interference to the controlling entity or anindication 605 of the interference or resource being used to theinterfering entity. The entity which receives the indication will thentake action to compensate for the interference 604 606. If the UEs areperforming direct D2D communications without the use of a controllingentity the UE which detects the interference may provide some form offeedback to the transmitting UE which provides an indication of theinterference. It would then be the responsibility of the transmitting UEto take action to avoid or compensate for the interference. In thefollowing examples, a D2D group with a controlling entity is presumed,however the techniques are equally applicable to direct D2Dcommunications between UEs.

FIG. 7 provides a flow diagram of an approach which is in accordancewith an example of the present disclosure where the source of theinterference detected at the UE is an eNodeB. As described withreference to FIG. 6, the UE initially receives a resource allocation 701from the controlling entity of its D2D group. Once this has beenreceived and D2D communications commenced, the UE sets up a measurementevent and monitors its allocated resources for interference.Interference monitoring may take place with respect to all or part ofthe resources which have been allocated to the UE. For example, in FIG.7 the UE monitors for downlink signals from an eNodeB which correspondto its allocated uplink resources. If the downlink signals whichcorrespond to such uplink resources have been detected 702, the UEattempts to establish an RRC connection 703 with the eNodeB. Uponestablishment of an RRC connection the resources currently being used bythe D2D group, and therefore the interference caused by the eNodeB, areindicated to the eNodeB via a measurement report message for example704. As an alternative to a measurement report message or other uplinkmessage, the indication may also be communicated via an RRC connectionrequest or another initial uplink message sent on an uplink channel,such as the random access channel (RACH) for example in order to avoid aconnection setup delay. Upon receipt of the indication the eNodeB has anumber of options of how to compensate for the interference. A firstapproach is illustrated in FIG. 7, where the eNodeB may cease using theresources which the D2D group is using and reserve these resources 705until they are no longer required by the D2D group. This approach may besuitable for public safety D2D communications because it does notinvolve the D2D group switching resources and it also ensure that theinterfering eNodeB will not interfere in the near future because theresources are reserved. In order for resources to be reserved correctly,further procedures such as synchronisation between the D2D group and theeNodeB may be necessary. For example, timing and frequencysynchronisation between the eNodeB and the D2D group may be required.

Although the approach illustrated in FIG. 7 and described above providea robust approach to allow a D2D to continue using a same set ofresources, a number of potential issues may arise. Firstly, becauseresources are allocated solely to D2D communications the capacity of thenetwork is adversely affected. Consequently, it would be beneficial froma network operator point of view that resources are reserved for afinite period of time but whilst allocation the reservation to berenewed by the D2D group if the resources are sill required upon expiryof the time period. In combination with expiry period it may also beadvantageous for a UE to inform an eNodeB when the resources allocatedfor D2D communications are no longer required. For instance this mayoccur when D2D communications have finished. Secondly, it may not bedesirably from a network operator point of view that UEs are able toexercise control over resource allocation and therefore an eNodeB. Thiseffect is lessened if resource allocation is only permitted for publicsafety application because situations where public safety emergenciesarise and network coverage is unavailable are hoped to be relativelyrare. To prevent UEs exercising undesirably levels of control ofeNodeBs, it is envisaged that only authentic public safety UEs are ableto initiate resource reservation at the eNodeB. Accordingly, some formof authentication may be required such as a security token or otherinformation that may be used to verify that the UE is an authenticpublic safety device.

The measurement event setup within the UE to detect interference mayeither be created internally at the UE or potentially configured by theUE's controlling entity such that all UEs within a D2D group apply thesame interference detection criteria. In terms of interference detectioncriteria there may be an interference level threshold or power levelthreshold which is required to be exceeded before a measurement event isreported. This would therefore allow UEs which are within a coveragearea of an eNodeB but which do not experience problematic interferenceto avoid requesting resource reservation. The measurement ofinterference from eNodeB may be measured via measurement of thereference signal received power (RSRP) or reference signal receivedquality (RSRQ) of the downlink eNodeB signal or the RSRQ of the D2Dcommunication signal. In order to reduce the quantity of datatransmitted to the eNodeB indicating the resources used by D2Dcommunications, the UE may provide a resource index which indicateswhich out of a predetermined range of resources the D2D group iscurrently using.

FIG. 8 provides a flow diagram of an approach in accordance with anexample of the present disclosure where the source of the interferencedetected at the UE is an eNodeB. The initial steps in the procedure areequivalent to those described above with reference to FIG. 7, however,the action that the eNodeB takes to compensate for the interferencediffers. Instead of reserving the resources which the D2D group iscurrently using and which have been indicated to the eNodeB, it isinstead the eNodeB that determines a set of resources which can be used801 by the D2D group and provides the UE with an indication 802 of thisrevised allocation. The UE will then be required to relay the indication803 of the revised resource allocation to the controlling entity ortransmitting UE so that the controlling entity or transmitting UE canconfigure the D2D group to use the newly allocated resources 804.Depending on the control structure of the D2D group, the reconfigurationof the resource allocation within the D2D group may take a number offorms. For example a new control channel may be established in the newlyallocated resources and UEs directed to this channel. Alternatively, anRRC reconfiguration command may be sent or a broadcast channel set up bythe controlling entity may be used to inform all UEs within the D2Dgroup of a change in resources, or the transmitting UE may simply startto transmit on a new resource requiring that receiving UEs reconfigureto this resource. Such reconfiguration data may also includesynchronisation information in order to synchronise the group with theeNodeB such that the resources are accurately allocated and interfacedue to poor synchronisation reduced. Although the approach illustratedin FIG. 8 transfer control of resource allocation to an interferingeNodeB, the D2D communications for public safety applications will stillhave priority over commercial communications. The resources allocatedfor D2D may be defined in terms of allocated bandwidth, time slots or acombination of both bandwidth and time slots.

FIG. 9 provides a flow diagram of an approach in accordance with anexample of the present disclosure where the source of the interferencedetected at the UE is a neighbouring D2D group or an uplink signal froma UE communicating with an eNB. As described with reference to FIG. 6,the UE initially receives an indication of a resource allocation 701from the controlling entity of its D2D group. Once this has beenreceived and D2D communications commenced the UE sets up a measurementevent and monitors its allocated resource for interference. Interferencemonitoring may take place with respect to all or part of the resourceswhich have been allocated to the UE but is most likely to be respect tothe resources allocated for uplink D2D transmissions by the UE. Thismeasurement event may be configured in a similar manner to thatdescribed with reference to FIGS. 7 and 8 but is not directed solely todownlink signals from an eNodeB. Once a measurement event has beendetected 901 there are a number of approaches which may be taken tocompensate for the interference. A first approach is the UE provides anindication of the interference to the its controlling entity asmeasurement report 902, where the indication may include interferencepower, frequency and the like. The controlling entity or transmitting UEmay then reconfigure the resources 903 which are utilised by the D2Dgroup such that the interference is substantially avoided. Thereconfigured resources may be selected from a predetermined set of D2Dresources or from the entire range of resources which the D2D group isoperable to operate over. An alternative and potentially moresophisticated approach is for the UE, once a measurement event has beendetected at the UE, to establish the source of the interference and inparticular whether its origin is a second D2D group. This is achieved bymonitoring the resources upon which the interference was detected for abroadcast signal 904 from a second D2D group. Each D2D group and inparticular each controlling entity of a D2D group may be configured toprovide broadcast information in a broadcast signal so that UE can jointhe D2D group. This broadcast information may include synchronisationand timing information and other configuration information required toestablish a connection with the controlling entity. All or part of thisbroadcast information may then be included in the indication 902provided to the controlling entity by the UE. With this information thecontrolling entity may then either adapt the use of the currentresources to substantially avoid the interference or reconfigure theresource allocation 903 as described above for the first approach.

FIG. 10 provides a flow diagram of an approach in accordance with anexample of the present disclosure where the source of the interferencedetected at the UE is a neighbouring or second D2D group and either thefirst D2D group or both D2D groups are within the coverage area of aneNodeB. As described with reference to FIG. 7, the UE initially receivesan indication of a resource allocation 701 from the controlling entityof its D2D group. Once this has been received and D2D communicationscommenced the UE sets up a measurement event and monitors its allocatedresource for interference. Interference monitoring may take place withrespect to all or part of the resources which have been allocated to theUE but is most likely to be respect to the resources allocated foruplink D2D transmissions by the UE. This measurement event may beconfigured in a similar manner to that described with reference to FIGS.7 and 8 but is not directed solely to downlink signals from an eNodeB.Once excessive interference has been detected 901 and a measurementevent occurred the UE establishes whether the interference results froma neighbouring or second D2D group. If so, the UE may then attempt toreceive broadcast information 904 transmitted by the controlling entityof the neighbouring or second D2D group in order to establish whetherthe second D2D group is within the coverage area of an eNodeB. If thesecond D2D group is out of coverage but the first D2D group is within acoverage area then the UE is configured to send an indication of theinterference 1001 to the controlling entity of the second D2D group sothat the resources of the second D2D network can be reconfigured 1002such that interference between the two D2D groups is reduced. Thisapproach allows independent D2D resource allocations to be reconfiguredbefore it is required to reconfigure eNodeB allocations and thereforeprevents UEs from determining resource allocations at an eNodeB.Although in FIG. 10 an indication of interference i.e. a measurementreport has been sent to the controlling entity of the second D2D group,if both the first and second D2D groups are within a coverage area of aneNodeB a measurement report may be sent to both controlling entitiessuch that both resource allocations are reconfigured. Alternatively, themeasurement reports may be relayed back to the eNodeBs which provide thecoverage for the first and second D2D groups such that thereconfiguration of resources can be negotiated between the eNodeBs via abackhaul link or the controlling entities and the eNodeBs.

Although the approaches described with reference to FIGS. 6 to 10 havebeen applied to D2D groups where a controlling entity configures andcoordinates communications within the group the above describedapproaches may also be applied to direct D2D communications without acontrolling entity as illustrated in FIG. 2a . In cases where there isno controlling entity, each UE may internally setup a measurement eventwhich monitors interference on the resources used for D2Dcommunications. If interference is detected, the UE which performed thedetection may then become responsible for reconfiguring the allocationof resources such that the interference is avoided or may report theinterference to the transmitting UE which would then reconfigure theresources being used for transmission. This situation may occur forexample where the interference originates from an eNodeB or aneighbouring D2D group to which the UE is unable to establishcommunications with therefore unable to request that their resourceallocation is reconfigured. Furthermore, even though the measurementevent have been described as applying to only a single type ofinterference i.e. either D2D interference or eNodeB interference, eachUE in a D2D group may monitor its resources for any type of excessiveinterference. For instance, a UE may detect interference from a devicewhich is neither a D2D device or an eNodeB but is instead for example aconventional UE which is communicating with an eNodeB, or anotherinterfering device entirely. In such a scenario the controlling entityof the UE or the currently transmitting UE may be informed of theinterference and resource allocations reconfigured to avoid theinterference.

De-Centralised Resource Allocation

A particular issue is as shown in FIGS. 11 and 12 showing differentscenarios. FIG. 11 provides an example in which a UE 1104 from a firstgroup of UE's 1101, 1102, 1103, 1104 experiences interference as aresult of a UE 1104 from that group moving into an interference coveragearea 1114 of transmissions of a second group of UE's 1106, 1107, 1109,1110. Correspondingly FIG. 12 provides an example in which the new EE1104 moves out of coverage area the interference region 1104 from thesecond group of unions.

If the controlling and/or transmitting UEs from two separate groups areunable to detect the signal from one another, or from UEs transmittingto an eNB, then a CSMA based or co-ordinated approach will not improvethe situation for a receiving UE which is receiving signals from bothtransmitting UEs without some form of feedback from a potentialreceiving UE. This can also be the case even when the UEs arestationary.

According to the example embodiment shown in FIGS. 11 and 12 there is nocontrolling entity provided in the respective groups of UEs. Accordingto the example shown in FIGS. 11 and 12 one of the UEs in each groupperforms a carrier sensing operation to detect interference fromtransmissions from one or more UEs in the other group. Having detectedthe interference, the UE transmits an indication of the interference toother members of the same group or the members of the other group of UEsand accordingly directs the transmitting UE to avoid the communicationschannel on which interference is caused by transmissions from the othergroup. FIG. 11 provides an example scenario which as a result ofmobility one of the UEs from the first group moves into coverage areaprovided by the second group. In the example in FIG. 12 one of UEs fromthe group which is interfering with the second group moves out of thecoverage area of the second group.

The transmitting UE needs to take into consideration whether or not thereceiving UEs are able to listen on the resource as well as whether thetransmitting UE can detect any possible interference. The actual methodof taking this information into account when allocating resources at thetransmitting UE will depend on the general approach taken.

-   -   If a control plane connection exists between a controlling        entity and other UEs then this could be used to convey        measurement reports either to a transmitting UE from a receiving        UE or via a controlling entity.    -   A purely broadcast approach may need to reserve specific        resources to allow UEs to send control information, or        prioritise attempts to transmit control information over data        transmissions.

According to this example the listener UE needs to be able to inform thetransmitting UE if it enters the coverage of a transmitting UE fromanother D2D group/session or into the coverage of an eNB. The method ofreporting will depend on the resource allocation method chosen andshould be taken into account when selecting the solution.

The following number paragraphs provide further example aspect andfeatures of the present technique:

Paragraph 1. A communications system comprising a plurality of acommunications devices and an infrastructure equipment, theinfrastructure equipment configured to communicate with one or more ofthe plurality of communication devices via a wireless access interfaceand the plurality of communications devices configured to performdevice-to-device communication with one or more others of the pluralityof communications devices via the wireless access interface and tocommunicate with the infrastructure equipment via the wireless accessinterface, and one of the plurality of communications devices isconfigured

-   -   to transmit data in resources of the wireless access interface        to one or more of the communications devices, wherein one or        more of the communications devices are configured    -   to detect signals in the wireless access interface from the        infrastructure equipment, the signals indicating potential        interference in the wireless access interface, and    -   to provide, in response to detecting the signals, an indication        of the resources of the wireless access interface to the        infrastructure equipment.        Paragraph 2. A communications system according to paragraph 1,        wherein the potential interference is in an uplink channel of        the wireless access interface.        Paragraph 3. A communications system according to paragraph 1,        wherein in response to receiving the indication of the resources        of the wireless access, the infrastructure equipment is        configured to reallocate resources of the wireless access        interface to compensate for the interference.        Paragraph 4. A communications system according to paragraph 1,        wherein in response to receiving the indication of the resources        of the wireless access, the infrastructure equipment is        configured to provide a resource reallocation message to the        data transmitting communications device, and the data        transmitting communications device is configured, in response to        receiving the resource reallocation message, to transmit data in        resources of the wireless access interface in accordance with        the resource reallocation message to compensate for the        interference.        Paragraph 5. A communications system according to paragraph 1 to        3, wherein one of the communications devices forms a controlling        entity for allocating the resources of the wireless access        interface to the communications devices.        Paragraph 6. A communications system according to paragraph 5,        wherein in response to receiving the indication of the resources        of the wireless access, the infrastructure equipment is        configured to provide a resource reallocation message to the        controlling entity, and the controlling entity is configured, in        response to receiving the resource reallocation message, to        reallocate resources of the wireless access interface in        accordance with the resource reallocation message to compensate        for the interference.        Paragraph 7. A communications system according to paragraph 1,        wherein the detected signals are in a downlink channel of the        wireless access interface from the infrastructure equipment, and        the downlink channel of wireless access interface and an uplink        channel of the wireless access interface from the communications        devices include at least some of the same resources.        Paragraph 8. A communications system according to paragraph 1,        where the indication is provided to the infrastructure equipment        via the wireless access interface.        Paragraph 9. A communications system according to paragraph 1,        wherein the indication of the interference is provided in        response to the signals in the wireless access interface        interference exceeding a predetermined threshold.        Paragraph 10. A communications device for        device-device-communications, the communications device        configured to perform device-to-device communications via a        wireless access interface with one or more other communications        devices of a group of communications devices, the communications        devices being configured to communicate with an infrastructure        equipment via a wireless access interface, the communications        device comprising    -   a transmitter configured to transmit data to one of more of the        communications devices of the group, and    -   a receiver configured to receive data from one of more of the        communications devices of the group, and    -   a controller configured in combination with the transmitter and        the receiver    -   to transmit data in resources of the wireless access interface        to one or more of the communications devices of the group,    -   to detect signals in the wireless access interface from the        infrastructure equipment, the signals indicating potential        interference in the wireless access interface, and    -   to provide, in response to detecting the signals, an indication        of the resources of the wireless access interface to the        infrastructure equipment in which the communications device is        transmitting the data.        Paragraph 11. An infrastructure equipment for communicating with        one or more communications devices via a wireless access        interface, the communications devices configured to perform        device-to device communications via the wireless access        interface with or more other communications devices, wherein the        infrastructure equipment is configured to    -   receive an indication of the resources of the wireless access        interface from one of the communications devices in which the        communications device is transmitting the data.        Paragraph 12. A method for performing device-to-device        communications between a plurality of communications devices and        infrastructure equipment, the infrastructure equipment        configured to communicate with one or more of the plurality of        communication devices via a wireless access interface and the        plurality of communications devices are configured to perform        device-to-device communication with one or more others of the        plurality of communications devices via the wireless access        interface and to communicate with the infrastructure equipment        via the wireless access interface, the method comprising    -   transmitting, by one of the plurality of communications devices,        data in resources of the wireless access to one or more of the        communications devices,    -   detecting, at one of the communications devices, signals in the        wireless access interface from the infrastructure equipment        which indicate potential interference in the wireless access        interface, and    -   providing, in response to the detected signals, an indication of        the resources of the second wireless access interface to the        infrastructure equipment in which the communications device is        transmitting the data.

Various further aspects and features of the present invention aredefined in the appended claims and various combinations of the featuresof the dependent claims may be made with those of the independent claimsother than the specific combinations recited for the claim dependency.Modifications may also be made to the embodiments hereinbefore describedwithout departing from the scope of the present invention. For instance,although a feature may appear to be described in connection withparticular embodiments, one skilled in the art would recognise thatvarious features of the described embodiments may be combined inaccordance with the disclosure.

The invention claimed is:
 1. A communications system comprising aplurality of communications devices configured to performdevice-to-device (D2D) communication via a wireless access interface, atleast one of the plurality of communications devices serves as acontrolling entity, wherein a first communication device of theplurality of communications devices is configured to: transmit D2D data,in resources of the wireless access interface allocated by thecontrolling entity, to a second communications device of the pluralityof communications devices operating within the coverage area and undercontrol of the controlling entity, wherein the second communicationsdevice is configured to detect signals in the wireless access interfacecausing interference in the resources of the wireless access interfaceused to transmit the D2D data; in response to detecting the signalscausing the interference, on a condition that an infrastructureequipment caused the interference, transmit to the infrastructureequipment an indication of the resources of the wireless accessinterface used to transmit the D2D data in a random access channel(RACH) message, and on a condition that an interfering entity caused theinterference, transmit to the controlling entity the indication of theresources of the wireless access interface used to transmit the D2D dataso the controlling entity takes action to compensate for theinterference, wherein the interfering entity is a neighboring D2D group.2. The communications system of claim 1, wherein the detected signalsare in an uplink channel of the wireless access interface used foruplink communications with the infrastructure equipment.
 3. Thecommunications system of claim 1, wherein in response to receiving theindication of the resources of the wireless access interface used totransmit the D2D data, the infrastructure equipment is configured toreallocate resource of the wireless access interface to compensate forthe interference.
 4. The communications system of claim 1, wherein inresponse to receiving the indication of the resources of the wirelessaccess interface used to transmit the D2D data, the infrastructureequipment is configured to provide a resource reallocation message tothe second communications device that transmitted the RACH message, andthe second communications device is configured, in response to receivingthe resource reallocation message, to transmit D2D data in resources ofthe wireless access interface in accordance with the resourcereallocation message to compensate for the interference.
 5. Thecommunications system of claim 1, wherein one of the plurality ofcommunications devices forms a controlling entity for allocating theresources of the wireless access interface to the communicationsdevices.
 6. The communications system of claim 5, wherein in response toreceiving the indication of the resources of the wireless accessinterface used to transmit the D2D data, the infrastructure equipment isconfigured to provide a resource reallocation message to the controllingentity, and the controlling entity is configured, in response toreceiving the resource reallocation message, to reallocate resources ofthe wireless access interface in accordance with the resourcereallocation message to compensate for the interference.
 7. Thecommunications system of claim 1, wherein the detected signals are in adownlink channel of the wireless access interface from theinfrastructure equipment, and the downlink channel of wireless accessinterface and an uplink channel of the wireless access interface fromthe communications devices include at least a portion of the sameresources.
 8. The communications system of claim 1, wherein theindication of the interference is provided in response to the detectedsignals in the wireless access interface interference exceeding apredetermined threshold.
 9. A communications device for device-to-device(D2D) communications, the communications device configured to performD2D communications via a wireless access interface with one or moreother communications devices of a group of communications devices, atleast one of the group of communications devices serves as a controllingentity, the communications device comprising: a transmitter configuredto transmit D2D data to one of more of the communications devices of thegroup; a receiver configured to receive D2D data from one of more of thecommunications devices of the group; and a controller configured incombination with the transmitter and the receiver to transmit D2D datain resources of the wireless access interface allocated by thecontrolling entity to one or more of the communications devices of thegroup operating within the coverage area and under control of thecontrolling entity; detect signals in the wireless access interfacecausing interference in the resources of the wireless access interfaceused to transmit D2D data; and, in response to detecting the signalscausing the interference, on a condition that an infrastructureequipment caused the interference transmit to the infrastructureequipment an indication of the resources of the wireless accessinterface used to transmit the D2D data in a random access channel(RACH) message, and on a condition that an interfering entity caused theinterference, transmit to the controlling entity the indication of theresources of the wireless access interface used to transmit the D2D dataso the controlling entity takes action to compensate for theinterference, wherein the interfering entity is a neighboring D2D group.10. A method for performing device-to-device D2D communications betweena plurality of communications devices via a wireless access interface,at least one of the plurality of communications devices serves as acontrolling entity, the method comprising: transmitting, by one of theplurality of communications devices in resources of the wireless accessinterface allocated by the controlling entity, D2D data to one or moreof the communications devices operating within the coverage area andunder control of the controlling entity; detecting, at one of thecommunications devices, signals in the wireless access interface causinginterference in the resources of the wireless access interface used totransmit the D2D data; in response to the detected signals causing theinterference, on a condition that an infrastructure equipment caused theinterference, transmitting to the infrastructure equipment an indicationof the resources of the wireless access interface used to transmit theD2D data in a random access channel (RACH) message, and on a conditionthat an interfering entity caused the interference, transmitting to thecontrolling entity the indication of the resources of the wirelessaccess interface used to transmit the D2D data so the controlling entitytakes action to compensate for the interference, wherein the interferingentity is a neighboring D2D group.
 11. A communications device forperforming device-to-device (D2D) communications via a wireless accessinterface with one or more other communications devices of a group ofcommunications devices, at least one of the group of communicationsdevices serves as a controlling entity, communications devicecomprising: circuitry comprising a processor and configured to transmitD2D data to another communications device in a first set ofcommunication resources of the wireless access interface allocated bythe controlling entity, wherein the another communications deviceoperates within the coverage area and under control of the controllingentity; detect signals transmitted in the first set of communicationthat cause interference with the first set of communication resources ofthe wireless access interface used to transmit the D2D data; and inresponse to detecting the signals causing the interference, on acondition that an infrastructure equipment caused the interference,transmit to the infrastructure equipment an indication of the resourcesof the wireless access interface used to transmit the D2D data in arandom access channel (RACH) message, and on a condition that aninterfering entity caused the interference transmit to the controllingentity the indication of the resources of the wireless access interfaceused to transmit the D2D data so the controlling entity takes action tocompensate for the interference, wherein the interfering entity is aneighboring D2D group.